Armored electrical cable



June 27, 1939. J. wg-rzHElSER Ef L 2,164,168

' Ammann mscnucm. cALE Original Filed May 15, 1935 fans-,e CoM/0L ana/wHaHa/var .so/vaga, ay

. B y mvmfmwff @9m-M. CWM Nm ATTORNEYS Patented June 27, 1939 UNITEDlSTATES PATENT OFFIQE ARMORED ELECTRICAL CABLE tion of New Jerseyoriginal application May 15, 1935, serial No.

21,524. Divided and this application October 4, 1935, Serial No. 43,530

Z Claims.

electrical failure as for instance, due to tearing l loose duringinstallation of any insulation on the conductors that might have adheredto the armor sheath.

Another object is to provide an armored cable of the above type, withadequate protection along 16 the entire exposed severed sharp edge ofthe sheath, and readily applied in installation of the cable, topreclude any possibility of cutting the insulation of the protrudingoutwardly turned conductors.

A feature 4of the invention is the use, preferably, of paraiiinimpregnated paper, applied about the insulating conductors, preferablyIby helical winding, the heat evolved in the assembly serving to softenthe wax and autogenously to bond the superposed convolutions to eachother.

Another feature is the superposition of another llayer of unwaxed orunparailined paper interposed between the bonded protective paper layerand the conventional outer helically wound metal armor sheath.

This application is a division of our pending application, Serial No.21,524, led May 15, 1935, and patented on October 29, 1935, under No.2,018,939.

In the accompanying drawing, in which are shown one or more of thevarious possible embodiments of the several features of the invention,

Fig. 1 is a. perspective view of a length of the armored cable, with theprotective bushing inserted,

Fig. 2 is a perspective vienr partly in longitudinal section, showingthe removal of a. por

` tion of the outer protective layer,

Fig. 3 is a view similar to Fig. 2 showing one step in the applicationof the protective bushing,

Fig. 4 is a view similar to Fig. 3, showing the final step in theapplication of the bushing,

Fig, 5 is a view in longitudinal cross-section showing the bushingapplied, and

Fig. 6 is a perspective view of the bushing as an article ofmanufacture.

Referring now to the drawing, there is shown an armored cableillustratvcly with two conductors I0 and il, each covered byconv-entional 55 insulation, illustratively braided covering i2.

The conductors are shown enclosed in an insulating protective covering,which is preferably a continuous spirally wound sheet of paper i3impregnated with wax, preferably parafiin. The Width of the paper isillustratively three times the pitch at which it is wound, so that thecoinpleted sheath will be three-ply. In the conventional process oifabricating the armored cable by winding the protective covering simultaneously with the armor sheath, the parafln or other wax becomessuiciently softened to aiord an adequate bond of the variousconvolutions and to eiect a secure continuous insulating enclosuresheath, and this without the need for special application of any form ofadhesive.

Irraddition to the bonded protective sheath, there is preferablyemployed, according to the present invention,I the further outerinsulating covering i4 of paper, devoid of wax or other adhesive, whichis wound about the inner protective sheath I3. About the parts thus fardescribed, is wound the conventional metal sheath i5 comprising a stripof metal wo :ad on a pitch substantially equal to its effective width,the overlapping helical edges being crimped together at i6.

In the armored cable made as described, the outer paper layer M is freefrom any adhesive bond with respect to the sheath and substantially freeof such bond with respect to the inner protective covering i3.Accordingly, no adhesive connection between the conductor or its protective covering and the outer metal sheath can occur, so that in bendingand manipulating the latter, there is no possibility of tearing looseany of the protective insulation, and electric failures from this causeare not apt to occur.

In use of the device, after cutting or severing the. sheath as at iladjacent the outlet box or other terminal structure, the outerinsulating layer i4 only is preferably removed down to a point slightlybelow the exposed end of the sheath, thereby to afford clearance for theinsulating bushing Winch may be of conventional construc tion. Thus, itis seen that the insulating bushing fits snugly in said clearance thusleft between the bonded protective sheath i 3 and the inner wall of themetallic armor i5. In constructions in which the entire insulatingprotection must be removed between the insulated conductors and themetal sheath, a simple fibre bushing may not fit with suiiicientsnugness to assure its retention, while an attempt to introduce abushing without removal of any of the insulating covering between theinsulated conductors and the metal armor usually involves diiculty.While, as above noted, a conventional bushing may he employed, we haveshown in Fig. 6 of the drawing one embodiment of the bushing, claimed inthe parent application, of which this is a division. This bushing isshown of helical conformation and of peripheral length somewhat greaterthan one complete convolution. The split ends i8 and I9 of the nbrebushing B are displaced longitudinally of the bushing along a pitch suchthat the trailing end 20 of the leading edge I9- overlaps tie leadingend 2| of the trailing edge I 8. The leading end I9' of the leading edgeI 9 constitutes a guiding conformation for ready installation of thebushing and the part of the bushing adjacent said leading edge I9becomes wedged or anchored in place in the application of the bushing,as best shown in Figs. 3 and 4. The leading rim 22 of the bushing ispreferably of pitch somewhat greater than that of the outer or trail-ingrim 23, as appears from the fact that the leading split edge I9 islonger than the trailing split edge I8. Preferably, the pitch of theleading rim 22 of the bushing is substantially equal to that of thehelically Wound sheath. and the trailing rim 23 which has an outwardlyturned flange 24 is of somewhat lesser pitch.

The application of the bushing is quite expedl tious, since it requiresnothing more than the single manipulation of introducing the leading oranchoring end I 9' with the thumb pushing it home to effect secureanchorage and then following with light pressure with the index andmiddle finger on the trailing rim 23 towedge it home.

The bushing thus securely wedgedl in place is effective around theentire periphery of the sharp severed edge of the armor sheath, so'thatthe construction avoids the objection to ordinary split insulatingbushings, in which protection is substantially lacking at the region ofthe split. In the present construction, the split region is in fact ofenhanced security, since a double layer of bre is presented thereat. y

It will thus be seen that there is herein described apparatus in whichthe several features oi this invention are embodied, and which in itsaction attains the various objects of the invention and is Well suitedto meet the requirements of practical use.

As many changes could be made in the above construction, and manyapparently widely difierent embodiments oi this invention could be made4Without departing from the scope thereof, it is intended that allmatter contained in the'above description or shown in the accompanyingdrawing shall he interpreted as illustrative and not in a limitingsense.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. An armored electric cable comprising one or more insulatedconductors, paraiiin paper .strip helically wound thereabout, said stripbeing wax impregnated and of width several times the pitch oi thewinding to present overlapping areas, the wax of said overlapping areasserving as the means for welding the saine together in a unitaryflexible structure, and a second helical strip of paper, free from wax,wound about said first strip, and a metal strip helically wound aboutthe pretectlve covering to form the armor sheath.

2. An armored electric cable comprising one or more insulatedconductors, a Wax covered paper strip helically wound in overlappingrelation about said conductors with the wax of said strip bonding theoverlapping areas thereof together in a substantially unitary flexibleinsulating sheath thereabout, an outer layer of protective paper freefrom adhesive, encircling said first covering, a helically wound metalsheath enclosing said protected conductors, whereby a split insulatingbushing frictionally may be retained in place between the armor andparaiiin paper protective covering in the space left by the removaldepth of such bushing.

JOSEPH WERTZHEISER. HARRY CHARMOY,

a()A of the outer paper layer for substantially the

